package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Service;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }

    //将传入的任何对象序列化后存入redis
    public void set(String key, Object value, Long time, TimeUnit timeUnit) {
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value), time, timeUnit);
    }

    //逻辑过期数据预热，对象写入
    public void setWithLogicalExpire(String key, Object value, Long time, TimeUnit timeUnit) {
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(timeUnit.toSeconds(time)));
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    //缓存击穿，查询
    public <R, ID> R queryWithPassThrough(String KeyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit timeUnit) {
        String key = KeyPrefix + id;
        //1. 从redis查询商铺缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //存在，返回商铺信息
            return JSONUtil.toBean(json, type);
        }
        //为空值
        if (json != null) {
            //返回错误信息
            return null;
        }
        //3.不存在根据id查询数据库
        R r = dbFallback.apply(id);
        if (r == null) {
            //将空值写入redis，预防缓存穿透
            stringRedisTemplate.opsForValue().set(key, "", time, timeUnit);
            //返回错误信息
            return null;
        }
        //7.存在，写入redis
        this.set(key, r, time, timeUnit);
        return r;
    }

    //线程池，10个线程
    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    //逻辑过期，查询
    public <R, ID> R queryWithLogicalExpire(String KeyPrefix, String LockKeyPrefix, ID id, Class<R> type, Function<ID, R> dbFallback, Long time, TimeUnit timeUnit) {
        String key = KeyPrefix + id;
        //1.从redis查询缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //判断是否存在
        if (StrUtil.isBlank(json)) {
            return null;
        }
        //命中,需要先把json反序列化为对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //未过期，直接返回店铺信息
            return r;
        }
        //已过期，需要缓存重建
        //获取互斥锁
        String lockKey = LockKeyPrefix + id;
        boolean isLock = tryLock(lockKey);
        //判断获取锁是否成功
        if (isLock) {
            //成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key, r1, time, timeUnit);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });
        }
        return r;
    }

    private boolean tryLock(String key) {
        //redis的setnx互斥命令：当redis中不存在key，才能在redis里set该数据
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
        return BooleanUtil.isTrue(flag); //避免自动拆箱带来的空指针问题
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }
}
